1. Field of the Invention
The present invention relates to a method for adjusting the lubricating time of a lubrication pump which is driven by a motor whose rate of rotation varies, particularly a direct current motor. The adjustment is carried out within a cycle time which includes the lubricating time and a non-lubricating time. The lubrication pump is used in the centralized lubrication of utility vehicles, including trailers, semi-trailers, special vehicles and the like. Preferably lubricants are utilized which are difficult to press and have a high penetration.
The present invention further relates to an apparatus for carrying out the above-described method. The apparatus includes a lubrication pump which is driven by an electric motor.
2. Description of the Related Art
In lubrication systems of the above-described type, direct current motor drives with a relatively low rate of rotation of 15 rpm are used. The tolerance of such motors is .+-.3 rpm. These tolerances are significantly increased depending upon the load exerted by the lubrication pump. This pressure, in turn, depends on the pressure of the lubricant, on the number of points to be lubricated, and particularly also on the prevailing temperature because the lubricants are substantially more viscous at low temperatures than at high temperatures.
In the past, the running time of the pump was adjusted in accordance with the time of operation of the vehicle involved. However, this does not take into consideration the above-mentioned changes of the rate of rotation and the attendant differences in the delivered quantities of lubricant. This means that there is always the danger of excess lubrication or too little lubrication.
It is, therefore, the primary object of the present invention to ensure that the necessary quantities of lubricant are supplied to the points to be lubricated even when the rate of rotation of the lubrication pump varies as explained above. In other words, it is to be prevented that too much lubricant reaches the points to be lubricated and that too little lubricant reaches the points to be lubricated.